All Blacks centre Sonny Bill Williams is reportedly set to announce he will return to rugby league next year following a stint in Japan.

According to the Australian Daily Telegraph, the 26-year-old has signed a A$800,000 (£528,000) 10-match deal with the Japanese rugby union side the Panasonic Wild Knights and a one-year contract with the Sydney Roosters for the 2013 National Rugby League (NRL) season.

The dual code international has long-been linked with a switch back to the 13-man code having sensationally walked out on Australian NRL side the Canterbury Bulldogs in 2008 to join French Top 14 side Toulon.

He returned to New Zealand in 2010 and signed with the Crusaders before helping the All Blacks claim the Rugby World Cup crown last year. A move to the Chiefs followed this season where he has been a key figure in the side's run to the New Zealand Conference title and the play-offs, but he is poised to turn his back on Super Rugby, temporarily at least, at the end of the current campaign.

The New Zealand Rugby Union has refused to confirm Williams' departure but a press conference is scheduled in Hamilton on Monday with the player and Chiefs coaches Dave Rennie and Wayne Smith along with All Blacks assistant coach Ian Foster.

The new Top League season in Japan is scheduled to begin at the end of August and as a result it would appear that Williams will be ruled out of the inaugural staging of the Rugby Championship and the end of year tour of Europe. Regulation 9 of the International Rugby Board's rules governing player release would still apply but New Zealand's strict policy of not selection players based overseas and the lucrative outlay taking Williams to Japan would make such a scenario highly unlikely.

The deal, that is also reportedly set to allow Williams to continue to pursue his boxing career at the same time, has been rumoured for some months with NZRU chief executive Steve Tew recently commenting: "We've put our position on the table for Sonny Bill. (Williams' agent) Khoder [Nasser] has respected that," Tew said.

"They've made whatever decision they've made in the full knowledge of what we could do and what we wanted to do and unfortunately we are bound by his desire to announce that on a timeline that suits him not us.''